Aquaponics Prawn and Tilapia

[JCO]

I've had no contact with Coyotes here in Fl., however I can tell you from seeing it with my own eyes, a Southeast Missouri Coyote can lope up to a 6' fence and clear it in full stride without touching it or loosing his stride. There use to be a $25. bounty on their hides in Missouri back in the early 70s and I hunted them rigorously because the country at that time was overrun with them.

They were quick, clever and not easily caught with their guard down. That's when I used my Remington model 700 BDL 22-250 rifle... 6 X 18 Redfield scope with adjustable parallax and Uncle Sam's benevolent training to take them out at 500 yds. without fail and always from downwind. I especially like hunting them in the winter when there was snow on the ground.

However it looks as though I have highjacked this thread. Sorry... I'm not following my own rules... now back to the regularly scheduled program....rabbits would be a better choice providing you can build the cages critter proof.

[rfeiller]

Tilapia are certainly the fish of choice, can't have them here and it would cost too much to maintain.

[TCLynx]

tilapia are not my fish of choice. I prefer fish that will survive my local climate without requiring heating to keep them alive (let alone eating or growing.)

I've found that in my systems the catfish grew just as fast or faster than the mixed gender blue tilapia and the catfish grew much larger. (easier to clean one catfish instead of 4 tilapia for a meal.) Anyway, now I'm growing some bluegill so I'll be able to compare their growth rates to the tilapia, if any of them are big enough to eat by December then I'll count them just as fast as my tilapia had been.

Only drawbacks is catfish and bluegill are not that interested in eating lettuce scraps.

[rfeiller]

yup the idea was to have a complete system, using the veggie scrapes to feed the tilapia along with the prawns once you raise any other fish you have an expensive food bill.

[TCLynx]

Well there are other things you can raise as fish food, like BSF larva, worms, crickets. In outdoor tanks/system I use bug lights over the tank to provide supplemental food as well.

[rfeiller]

i have koi and goldfish, i will supplement the feeding with worms when the worm buckets are built up enough. it would be easier if they were primarily herbivorious. heating the water is what the "cost to much to maintain" statement in my previous post was about. I can't maintain the gold fish at the level of polution that tilapia can exist at either. i started loosing koi and 6" goldfish when the nitrates hit about 200ppm in 1000 gal vat. did a 50% water change trying to save the remaining ones. it weakened them to the point that they have broken down. catfish are tough, but i don't eat them. i am thinking about going with blue gill. the nutrient level in the vat only hit a little over 500 on the conductivity meter not the 2000ms suggested in backyard systems.

[urbanfarmer]

i have koi and goldfish, i will supplement the feeding with worms when the worm buckets are built up enough. it would be easier if they were primarily herbivorious. heating the water is what the "cost to much to maintain" statement in my previous post was about. I can't maintain the gold fish at the level of polution that tilapia can exist at either. i started loosing koi and 6" goldfish when the nitrates hit about 200ppm in 1000 gal vat. did a 50% water change trying to save the remaining ones. it weakened them to the point that they have broken down. catfish are tough, but i don't eat them. i am thinking about going with blue gill. the nutrient level in the vat only hit a little over 500 on the conductivity meter not the 2000ms suggested in backyard systems.

200 PPM nitrate??? I had goldfish at over 1000 PPM nitrate with no noticeable signs of distress. They were like this for about 3 months. They were young though, but I bought the feeder comet goldfish from the pet store. At the pet store, they keep the water quality pretty low so the ones that survive are tough. I guess it's Darwinism. I still have these guys today and they are all over 6" in size. Some have even reproduced. I examined one yesterday and he was producing milt.

I'm honestly not sure though if my fish have strong genetics for surviving high ammonia, nitrite, and nitrate levels or if nitrate itself is just not toxic. The fish I am talking about were bombarded with urine on a daily basis. Ammonia and nitrite were spiked through the roof and so was the nitrate. I WAS trying to kill them. Only 1 died out of 40 in a 10 gallon tank. No water changes. To this day I think the feeder comet goldfish are the toughest fish, tougher than tilapia, but again it could have just been because they are kept in poor conditions and only the toughest survive...

[TCLynx]

Nitrates as measured by an aquarium test kit are generally not very toxic to fish unless you are talking a really high level for a really long time. RAS often has 500 ppm of nitrates since it costs them money to change out water so they only do the minimum.

If you are talking ppm of nutrient like measured with a hydoponic meter (EC, CF or TDS) well those are actually measuring the electrical conductivity of the water and they are only estimating nutrient strength based on the conductivity of the salts involved in hydroponic nutrients and those meters have very limited usefulness in aquaponics. My system (unless I've lately added sodium chloride to deal with moving fish or a fish disease)
will usually measure about 0.4-0.6 on the EC scale of my bluelab truncheon which corresponds to 200-300 ppm with the ECx500 ppm scale or it would be 4-6 on the CF scale which is 280-420 on the ECx700 ppm scale. What does all this mean? pretty much nothing, just means there is still a tiny bit of salt in the system like 0.2 ppt.

After adding salt to the system to like 3 ppt because of say an outbreak of illness in the fish or getting new fish to add to the system, that truncheon is going to read off the scale and I would have to water down a sample by 50% in order to get an accurate reading that I could then multiply by two which if it were hydroponic nutrient and I had that reading all the plants would be dead (as well as the fish) and if we were talking hydroponics and I got the low normal reading, I might as well be running plain water. but this isn't hydroponics.

Anyway, I know of people who have had all sorts of types of fish in a system with really high nitrates. My nitrates have run well over 200 ppm (like I was having to dilute samples to get an accurate reading and then multiply to know how high my nitrates were, up around 400 at times and the catfish survived great. The ammonia and nitrites were kept below readable levels and my pH was high which I suspect is why my plants were not as good at using up the nutrients and I had high nitrates, even then the EC meter would tell me a low number unless I had salted the system.

[cedarswamp]

1000 PPM nitrate and you call the pet stores water quality low? jk

i have koi and goldfish, i will supplement the feeding with worms when the worm buckets are built up enough. it would be easier if they were primarily herbivorious. heating the water is what the "cost to much to maintain" statement in my previous post was about. I can't maintain the gold fish at the level of polution that tilapia can exist at either. i started loosing koi and 6" goldfish when the nitrates hit about 200ppm in 1000 gal vat. did a 50% water change trying to save the remaining ones. it weakened them to the point that they have broken down. catfish are tough, but i don't eat them. i am thinking about going with blue gill. the nutrient level in the vat only hit a little over 500 on the conductivity meter not the 2000ms suggested in backyard systems.

200 PPM nitrate??? I had goldfish at over 1000 PPM nitrate with no noticeable signs of distress. They were like this for about 3 months. They were young though, but I bought the feeder comet goldfish from the pet store. At the pet store, they keep the water quality pretty low so the ones that survive are tough. I guess it's Darwinism. I still have these guys today and they are all over 6" in size. Some have even reproduced. I examined one yesterday and he was producing milt.

I'm honestly not sure though if my fish have strong genetics for surviving high ammonia, nitrite, and nitrate levels or if nitrate itself is just not toxic. The fish I am talking about were bombarded with urine on a daily basis. Ammonia and nitrite were spiked through the roof and so was the nitrate. I WAS trying to kill them. Only 1 died out of 40 in a 10 gallon tank. No water changes. To this day I think the feeder comet goldfish are the toughest fish, tougher than tilapia, but again it could have just been because they are kept in poor conditions and only the toughest survive...

[rfeiller]

the reference to the conductivity of 2000 is what is stated in the "backyard and hobbyist systems" article in this website. it is the standard for hydroponics. i know salt increases conductivity. i was just puzzled at 200ppm nitrates and conductivity of a little over 500 with a target of 2000 in aquaponics according to the article, assuming that it was the target for aquaponics.